As activists push states to recognize gay marriages, New Jersey Gov. Chris Christie — conservative Republican governor in a blue state and a 2016 presidential possibility — is walking a fine line between two electorates and two elections.

Christie vetoed same-sex marriage legislation last year and severely criticized the Supreme Court’s decision striking down a ban on federal rights for same-sex married couples. At the same time, he is “adamant” that same-sex couples deserve equal legal protection, wants a referendum on gay marriage, and vows to abide by a same-sex marriage law if New Jersey voters approve it.

He’s tiptoeing between constituencies. First are the voters of New Jersey: polls show they favor same-sex marriage, and Christie wants them to reelect him in November by a big margin.

Then there are Republican caucus-goers in Iowa. Christie needs their backing if he runs for president in 2016; in 2012, evangelical conservatives, who generally oppose gay marriage, made up 57 percent of Republican caucus-goers in the state, according to exit polls.

And there is a third group of voters to think about: swing voters across the nation, who might go for a Republican presidential nominee who is sufficiently centrist.

To appeal to those voters, Christie “will want to not be perceived to be as far right as many Republicans are,” says David Boaz of the Cato Institute, a libertarian think tank. “That’s a lot of tightropes to walk.”

Christie, who is Roman Catholic, has said he does not believe being gay is a choice, nor is it a sin, and that he has gay friends who argue the issue with him. Marriage, he said last year on CNN, is “special and unique in society.” He followed his veto in of the gay-marriage bill in February 2012 with a call for a statewide referendum on whether to allow same-sex marriage by constitutional amendment.

“When you want to change the core of a 2,000 year-old institution, the way to do that is to put it in front of the voters,” he told reporters July 2.

A referendum would allow same-sex marriage to pass in New Jersey without his fingerprints — or as he said at a town-hall-style meeting last month: “I don’t have to compromise my principles that I believe in and someone else doesn’t have to compromise theirs.”

Christie is in the same position as his party. The Republican platform says marriage is only for couples of the opposite sex, but Chairman Reince Priebus has said that the Republican Party should be open to those who favor same-sex marriage. “I don’t believe we need to act like Old Testament heretics,” he told USA TODAY in March. Instead, Republicans “have to strike a balance between principle and grace and respect.”

Garden State Equality, a leading advocate for same-sex marriage in New Jersey, opposes a referendum, saying civil rights should not be on the ballot. “It should never be up to the majority to vote on the rights of the minority,” spokesman T.J. Helmstetter said.

Same-sex marriage advocates are now lobbying New Jersey legislators to override Christie’s veto before the end of the year, when the window to do so expires. Christie is too powerful a party leader to let that happen, says Ben Dworkin, director of Rider University’s Rebovich Institute for New Jersey Politics.

“I can’t envision a situation where the Republican votes that are needed to get the two-thirds override would come, given this administration’s history,” Dworkin says. “The Christie administration sees no reason why any Republican should really ever override a Republican governor. That’s their logic, so I’d be shocked if it ever got to happen.”

Last year, Christie nominated a gay judge (a Republican) to the state Supreme Court, a first for the state. Last month, when the Supreme Court ruled on Defense of Marriage Act, he called it “insulting” to the Congress and president that passed the law.

Troy Stevenson, executive director of Garden State Equality, said, “I don’t like to pretend I can get inside the mind of the governor, but I think the closer we get to him having future political ambitions the more staunch his opposition gets to marriage equality.”

But Jimmy LaSalvia, a founder of GOProud, a Republican gay-rights group that favors same-sex marriage, gives Christie credit for not trying to change the subject.

“He’s one Republican who doesn’t say ‘I believe marriage is between a man and a woman. We need jobs and the economy is hurting,”’ says LaSalvia, who now works with the ACLU trying to pass same-sex marriage state by state. “He’s willing to talk through the issue in a way that no other Republican has the balls to do.”

Christie has to make his political calculus now, even though “he doesn’t know how much public opinion will change between now and 2016,” Boaz said. “Will people be more liberal then? Is the country? Yes. But the Republican primary electorate, maybe not so much.”

Public opinion on gay marriage has changed rapidly. Four years ago, 37 percent of Americans favored same-sex marrage. Now, 51 percent do, according to the Pew Research Center.

Iowa and New Hampshire, traditionally the first states to hold presidential nominating contests, both allow same-sex marriage – which could mean voters there no longer focus on it as an issue.